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Trying to understand the PID on my lelit pl041tqe
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jwark
Senior Member
jwark
Joined: 29 Dec 2012
Posts: 42
Location: TX
Expertise: I live coffee

Espresso: Le'Lit PL041TQE
Grinder: Le'Lit PL53
Posted Sun Jan 6, 2013, 8:57pm
Subject: Trying to understand the PID on my lelit pl041tqe
 

So, I noticed the temp drops down really fast after I pull a shot. After researching I believe I am understanding that is because it is only measuring the temperature at the steam head and the water behind that is still colder. In short, I guess I need to let it heat up more?

So, the PID does stop the boiler from heating the water when it reaches the desired temp, correct? So, then I have to wait for the water at the steam head to cool before it starts heating it up again? I was wondering if there is a more efficient way to get the water heated up faster? How would it work without a PID? Isn't something shutting it off when it reaches a certain temperature anyway? I wish I could understand a bit more exactly how the water temperature works. Also, where is being heated up at exactly? On the bottom or right at the steam head?

I did try to read some info on pids but I feel I have a lot of holes in my knowledge. Maybe if someone knows a good resource they could show me.

 
“It takes a big man to cry, but it takes a bigger man to laugh at that man.”  - Jack Handy
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D4F
Senior Member


Joined: 15 Mar 2012
Posts: 2,015
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Sun Jan 6, 2013, 9:27pm
Subject: Re: Trying to understand the PID on my lelit pl041tqe
 

A PID will stabilize the temperature at the sensor, wherever it is placed on that machine.  It is usually placed at a point of incoming cool water so that it calls for heat.  Heat is added as called for by PID to maintain idle temperature and to increase temperature after incming cool water.  With ambient loss there are small blips of heat.  Many add a blip of heat in portion of 2 second cycles, the sample interval.  Is is often not a direct measure of water temperature, I do not have a diagram of your machine.

The PID device is a temperature controller with P, I, and D algorithms.  P is a sampling interval as a proportion of the sensor range, but basically comes down to the temperature range that is acts on.  This is a setable range around the set temperature.  Make the interval and the device acts over a large range and may slow response.  Make it small and it does not have enough range for control.  On a generic PID device there is also alarm set temperature that is not damped and is temperature on and off switch and the temperature will over and undershoot.

Search PID and you will find some general articles that may better explain.

Click Here (www.datatrackpi.com)

Read and ask again, happy to help.

 
D4F also at
http://www.gaggiausersgroup.com/
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jwark
Senior Member
jwark
Joined: 29 Dec 2012
Posts: 42
Location: TX
Expertise: I live coffee

Espresso: Le'Lit PL041TQE
Grinder: Le'Lit PL53
Posted Sun Jan 6, 2013, 10:25pm
Subject: Re: Trying to understand the PID on my lelit pl041tqe
 

Thanks. I guess I need to first understand how the machine itself works. I can't really put anything into context without knowing that.

So what does that mean if the temperature drops when I pull a shot? That I just didn't let it warm up enough?

 
“It takes a big man to cry, but it takes a bigger man to laugh at that man.”  - Jack Handy
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D4F
Senior Member


Joined: 15 Mar 2012
Posts: 2,015
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Mon Jan 7, 2013, 10:39am
Subject: Re: Trying to understand the PID on my lelit pl041tqe
 

It means that hot water is leaving the boiler and cold water replacing it.  The drop seen initially is the drop at the sensor, PID temperature not whole boiler, where cold water is coming in.  You could likely turn off the machine for 30 - 60 seconds so that no heat comes in and then turn it on and see a temperature rise from that low as the water mixes.  The sensor is placed to be hit with cold water and start heating.  

It can also suggest that you did not reach thermal stability or warm up long enough.  I like 15 - 30 minutes on my Gaggia.

 
D4F also at
http://www.gaggiausersgroup.com/
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takeshi
Senior Member
takeshi
Joined: 12 Oct 2002
Posts: 976
Location: Houston
Expertise: I live coffee

Espresso: Alex Duetto 3.0
Grinder: Super Jolly
Roaster: Amaya Roasting
Posted Mon Jan 7, 2013, 2:27pm
Subject: Re: Trying to understand the PID on my lelit pl041tqe
 

D4F Said:

It means that hot water is leaving the boiler and cold water replacing it.

Posted January 7, 2013 link

^ This.  It's probably normal.  The heating element on your boiler isn't going to be able to instantly heat water coming in from the reservoir.  It would help if you would mention how much it drops as you're pulling a shot and how your shots are turning out.  If the water at the grouphead is too cool you'll definitely notice it in the cup.  Keep in that the temp at the sensor and the temp at the grouphead are two different things.  A drop in the former doesn't indicate a drop at the latter.

jwark Said:

In short, I guess I need to let it heat up more?

Posted January 6, 2013 link

If you're not giving the machine 30 minutes or so (can vary a bit by machine) to come up to temperature then, yes, you will need to let it warm up.  However, even so you're going to see a temp drop when the pump brings in water from the reservoir.  I can't recall off the top of my head but there's a reason why PID's don't monitor the temp at the grouphead and monitor the temp at the boiler.  IIRC you're relying on the thermal stability of the espresso machine when pulling a shot.

jwark Said:

I was wondering if there is a more efficient way to get the water heated up faster?

Posted January 6, 2013 link

Why do you think you need a more efficient way?
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